New vistas in the biological world have been revealed through the use of molecular techniques for assessing microbial diversity. Despite this revelation, whole division-level groups of bacteria exist in natural environments that are refractory to cultivation and potentially harbor previously undiscovered antibiotics. This study will access the functional diversity within the novel division Acidobacterium for the discovery of antibiotic agents. Using a collection of genomic clones derived from bacteria within this division, a heterologous expression system will be developed. By separating soil genomic DNA on the basis of G+C content, DNA fractions enriched for the presence of G+C content, DNA fractions enriched for the presence of Acidobacterium genomes will be used for genomic library construction in a broad host-range cosmid. Screening of this Acidobacterium-enriched genomic library for clones with activity against important human pathogens may result in the isolation of novel antibiotic agents, the genetic determinants and chemical structure of which will be determined.